LECTURE 20 PELVIC AND HIP JOINT JOINTS OF THE PELVIS - S shaped column is designed so that the weight is dissipated across the S shape - The centre of gravity – goes just anterior or just posterior to the joint - There is less degenerative change on the joint - Lumbosacral o Weight transferred just anterior to the lumbosacral joint, then transferred lateral to hip joints, then falls anterior to knee joint and significantly more anterior to the ankle joint o Secondary cartilaginous IV joint (IVD is thicker on the anterior side and thinner on the posterior side – allows lordosis to take place ) § Typical secondary cartilagionous joint; There is hyaline cartilage on both sides, and there is fibrocartilaginous disc in the middle (IVD)Joints of the pelvis o Synovial zygapophyseal joints – between the articular facets; has superior and inferior articular facets; encircling of synovia membrane + Lumbosacralcapsule Lumbosacral - Sacroiliac Seondary cartilaginous IV joint oSynovial Sacroiliac synovial joint b/w zygoapophyseal auricular joints surface of sacrum and ilium Sacroiliaco Strong weight -bearing joint o Synovial joint (but sometimes can be Sacroiliac synovialdescribed as part synovial and part joint b/wsyndesmosis) auricular surface of sacrum and oilium Syndesmosis – fibrous joint where two Pubic symphyseal Strongbones meet up at an interosseous weight-bearing joint membrane such as in the forearm Pubicbetween radius and ulna, and between symphyseal tibia and fibula Secondary cartilaginous Sacrococcygeal o The anterior bit is a synovial joint and b/w pubic bones the posterior bit is a syndesmosis - Pubic symphyseal Sacrococcygealo Secondary cartilaginous b/w pubic bones b/w(has a disc between them) sacrum and coccyx - Sacrococcygeal: b/w sacrum and coccyx – also secondary cartilaginous) Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM Pelvis. Articular Systems LUMBOSACRAL JOINTS Frame 7. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9 - When you go from one region to another, there are typical characteristics of vertebrae in each region; but there are transitional vertebrae between regions - In the lumbar region – the articular facets are in the sagittal plane - When L5 meets with S1 – has transitional characteristics – mix of lumbar and sacral - L5 + S1 o Inferior articular fact of L5 – laterally and anteriorly oriented (oblique shape) in the coronal plane o S1 corresponds to L5 – postero-medially oriented o Thus able to flexion up to L5; at L5, the inferior facets lock the entire vertebral column relative to sacrum o Don’t have anterior displacement of the entire vertebral column o Important for upright posture o Synovial - Ligaments: ilio-lumbar ligaments on the top; from transverse process of L5 to the iliac crest o lumbosacral ligaments on the bottom: from transverse L5 to iliac fossa Lumbosacral joints o stabilizing ligaments, and also strengthen SACROILIAC JOINT Sacroiliac joint Sacral tuberosity Interosseous Iliolumbar Anterior Posterior Sacroiliac Greater sciatic foramen Sacrospinous Lesser sciatic foramen Sacrotuberous - sacrum meets with iliac part of pelvisNetter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. Plate 340. Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM Pelvis. Articular Systems New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9 Frame 6, 7. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9 - there are two parts - the anterior bit – auricular region of the iliac - there is corresponding auricular region on sacrum (looks like an ear) - the sacrum meets with the pelvis in the auricular region - posterior to this, there is a sacral tuberosity - there are two parts to the articular face - the auricular surface has corresponding grooves + bumps – when sacrum meets with ilium, forms a closure; this part is the synovial part of joint (anteriorly) - posterior part of the joint, at the sacral tuberosity – there is an interosseous membrane where sacrum meets ilium; this is the syndesmosis part of the joint - important because when weight is transferred down, it goes anterior to L5/S1 joint; S1 has bony projection on anterior side called the sacral promontory o when weight is transferred, there is Tendency for sacrum to take weight and have a downward tilt into the pelvic cavity o The ligaments stop too much rotation happening in the sacrum o Thus sacroiliac joint is Important for weight bearing in an upright structure Ligaments for sacroiliac joint - Interosseous ligament – most important - Accessory ligaments – the ilio-lumar ligaments works as accessory ligament o Anterior and posterior sacroiliac ligaments – the interosseous ligament lies between this space between the sacrum and the ilium o Sacrotuberous + sacrospinous; § sacrotuberous – go from the sacrum to the ischial tuberosity § The sacrospinous ligaments also end up being accessory ligaments – to the ischial spine o Make the notches (greater and lesser sciatic notches) into foramina o They are accessory ligaments because o When you walk, there is compressive forces from the ground; in upright posture in bipedal human, ligaments take up a lot of the compressive forces that get transmitted upwards from the ground o When the compressive forces get transmitted upwards, there is tendency for the sacrum to rotate o The ligaments help keep sacrum in position MECHANISMS OF PELVIS - gravity falls at the L5/S1 joint Mechanism of pelvis - The shape of pelvis relative to line of gravity is oblique - The pubic symphysis ends up being the floor of the pelvic cavity, not the anterior wall - Pelvic cavity is tilted when you are standing upright - This means that the weight is transferred, the sacrum tends to turn/ rotate into the pelvic cavity - The rotation Is centred at S2 - Inward tilting = nutation (nodding) Nutation and counter-nutation - When this happens, the sacrum and the Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM Pelvis. Articular Systems Frame 6, 7. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9 Kapandji, A. 1982. Physiology of the joints, Vol. 2 sacral promontory falls inward - When this happens, the pelvic inlet gets smaller; The pelvic outlet gets to be bigger .